Gen Pershing had a solution for these terrorists:
http://www.snopes.com/rumors/pershing.asp
You need to read beyond the first paragraph of this Snopes article. They basically debunk the claim that Pershing did this or that it’s effective.
Debunking Islam itself is a far better tactic. People armed with the truth should at least be able to ensure that thoughtful, intelligent, and humane people all over the world reject Islam and/or apostasize. Then we only need to be worried about the child molestors, sociopaths, and violent criminals that are drawn to that fake religion, but by then we can treat them as enemy combatants.